DR650 static sag

[Bass]

This should perhaps be in the suspension thread, but I think it's more likely to reach someone who knows, over here.

I suspect the rear preload on my DR is too low. I have increased it once but with even a small amount of luggage on the back, the bike is still only just stable on the side stand.

Can anyone advise me as to what the rear end static sag should be for the stock suspension?

[Crisis management]

Bass, you know my bike and it's suspension....thats a stock spring wound up as hard as possible.
According to the manual, spring preload length (on the shock but out of the bike) is:
Soft: 253.5mm
Standard: 247.5mm
Stiff: 238.5mm

With my bike, unloaded but with the spring on the stiff setting, the static sag (bike only) is 30mm measured at the top of the rear guard behind the seat.
Now, I have always found that a hard setting for the road but I only weight 67kgs and the bike rides better with another 15kgs of luggage (less steering wander).
However, since my excursion off road on it I would say the springing is too soft as it almost bottomed over small whoops and I certainly wasn't going fast.

Sooo, if your loading it up, I'd look at a better spring. Nordie has fitted Eibach springs to his from Kientech engineering, I would look to his advice for reliable information.

[tri boy]

I'll have a guess at it mate.
Without a rider on board, and the bike unladen, I think the rear should sag approx 15-20mm.
With rider, and load, I'm guessing a sag of 40mm-60mm should be acceptable. RT would be one of the guys to correct these fiqures, but it sounds like the rear spring in your bike is struggling with it load.:mellow:
Assuming all links etc are in good order, it may be service time for your shock.

[NordieBoy]

Assuming all links etc are in good order, it may be service time for your shock.

Nope, that's what the standard spring does.

I'm running about 5cm of static sag at the moment as the lack of rebound damping pogo's the back up too high for comfort with less sag.

[Bass]

I'll have a guess at it mate.
Without a rider on board, and the bike unladen, I think the rear should sag approx 15-20mm.
With rider, and load, I'm guessing a sag of 40mm-60mm should be acceptable. RT would be one of the guys to correct these fiqures, but it sounds like the rear spring in your bike is struggling with it load.:mellow:
Assuming all links etc are in good order, it may be service time for your shock.

Mate, the bike has only done 1700 miles from new.

Ian's spring length measurements in the previous post may be of use as I suspect the original settings are well out. I haven't measured it yet but I will bet that the current static sag is about 70 mm and probably about 80 with some baggage aboard.

I will have a measure up tonight and tell all tomorrow.

RT is involved already and the bike will be getting a full Ohlins conversion early next month in preparation for the OZ trip and the much bigger load on the bike.

Your static sag unladen numbers are about what I would expect for a road bike with less travel than the DR. I have learned (to my cost) in recent times, that if the static sag is too low, then you can be forced to really crank up the rebound damping to stop the shock "Topping Out". I had thought that for an adventure bike, the numbers should be higher for the same reason. However, I certainly stand to be corrected and thanks for the input.

[Bass]

Bass, you know my bike and it's suspension....thats a stock spring wound up as hard as possible.
According to the manual, spring preload length (on the shock but out of the bike) is:
Soft: 253.5mm
Standard: 247.5mm
Stiff: 238.5mm



Thanks for that, but tell me, I would have thought that it is the shock which restricts the suspension travel. If so, then jacking the bike up should allow the shock to reach its maximum length. I am referring to your "on the shock but out of the bike" comment off course.
Have I got this wrong?
Is there something else which restricts suspension travel so that the shock cannot reach its max length when fitted?

[Bass]

Nope, that's what the standard spring does.

I'm running about 5cm of static sag at the moment as the lack of rebound damping pogo's the back up too high for comfort with less sag.

Thank you sir

I was kinda expecting to get answers in the 35 to 50 mm range, but thinking that it might be more because the shock response is average at best. As mentioned above, it should be a temporary situation and sorted next month.

[ducatijim]

I told u the stocker is typical; budget,mass produced jap-crap, like most things from japinc, made to a price not a purpose.

We both know the Ohlins will fix her.:yawn:

[Bass]

I told u the stocker is typical; budget,mass produced jap-crap, like most things from japinc, made to a price not a purpose.

We both know the Ohlins will fix her.:yawn:

True, but eight grand for a brand new bike is pretty good value and so I figure I can't moan too much.
The problem I have is a minor one - just an annoyance really, and I figure that if I can sort it with a minor adjustment, well why not?
Having said that, adjusting the preload is actually a bit of a pain.

[Crisis management]

Thanks for that, but tell me, I would have thought that it is the shock which restricts the suspension travel. If so, then jacking the bike up should allow the shock to reach its maximum length. I am referring to your "on the shock but out of the bike" comment off course.
Have I got this wrong?
Is there something else which restricts suspension travel so that the shock cannot reach its max length when fitted?

You are correct, the shock at full extension is the same as full extension of the bike suspension. I merely wanted to be clear that the measurement was of an unloaded shock, not an unloaded bike.
Clear, or would you like some muddy water with that? Obfustication is one of my middle names!
I'd love to try the bike when you get the Ohlins on, it'd be good to see a real comparison. Feel like a ride to Raglan?

[Bass]

You are correct, the shock at full extension is the same as full extension of the bike suspension. I merely wanted to be clear that the measurement was of an unloaded shock, not an unloaded bike.
Clear, or would you like some muddy water with that? Obfustication is one of my middle names!?

NO, that's just fine and it means I can do the measurement on the bike - I just need to make sure she's at full stretch.


I'd love to try the bike when you get the Ohlins on, it'd be good to see a real comparison. Feel like a ride to Raglan?

You're on, but be aware that it will be sprung for the "loaded for OZ" condition. This may mean that the springs are too stiff for ideal performance without that load. Reducing the preload may not entirely cure it if this turns out to be the case. Further, we will not be able to totally cure it by just adding load because the front will be sprung for the big safari tank which won't be fitted until we get to OZ.

Of course having said that, there will be times when the safari tank is close to empty and will weigh less than the standard one - so I would be disappointed if this turns out to be a problem.

[ducatijim]

True, but eight grand for a brand new bike is pretty good value and so I figure I can't moan too much.
The problem I have is a minor one - just an annoyance really, and I figure that if I can sort it with a minor adjustment, well why not?
Having said that, adjusting the preload is actually a bit of a pain.

And once u have tightened the preload, remember to increase the rebound damping........................................... ........................???:doh:

Boing...boing....boooing:......................... ...................:(

[Bass]

And once u have tightened the preload, remember to increase the rebound damping........................................... ........................???:doh:

Boing...boing....boooing:......................... ...................:(

Maybe.
I don't think that I have a problem with damping rates at the moment, just the ride height.

[cooneyr]

And once u have tightened the preload, remember to increase the rebound damping........................................... ........................???:doh:

Boing...boing....boooing:......................... ...................:(

Without a shock out revalve this cant be done on a DR650 which is a real pain as the standard rebound is to low (well I recon it is anyway).

Cheers R

[chris]

However, since my excursion off road on it I would say the springing is too soft as it almost bottomed over small whoops and I certainly wasn't going fast.
You can do what you want to the stock suspension before heading into the bush, it won't make a scrap of difference. My DR is no fan of the Woodhill whoops...

[ducatijim]

Without a shock out revalve this cant be done on a DR650 which is a real pain as the standard rebound is to low (well I recon it is anyway).

Cheers R

Oops, too far out in left field.:Oops:

I own one and know well the shortcomings of the Japinc suspension.

My comment was sarcastic.:whocares: As Bass well knows.

If you increase the preload, the rebound damping will need to be increased to reduce the classic 'DR pogo', encountered with any bump in the surface bigger than a dead midge.:done:

[Bass]

Right, for anyone who is interested, the static sag was 50mm with a spring length of 246 mm.

It's now 35 mm with a spring length of 239mm and will come back to about 50 mm with some baggage aboard.

This actually ties in quite well with the numbers that both Nordie Boy and Crisis Management suggested.

The bike is significantly more stable on the side stand too so, objective achieved. We will see what the ride is like on the weekend, but since all I have done in effect, is change the ride height, I don't expect to feel any difference.

However, ROLL ON MR OHLINS.

Oh and Jamie mate, at the risk of my accomodation for tomorrow night and just to be my usual anal self for a moment, increasing the preload does not of necessity mean an increase in rebound damping because it does not affect the spring stiffness in any way. The main effect is to increase the ride height.
However the 2 adjustments tend to be linked because the most common reason for a preload increase is more weight on the bike and very often, the extra weight requires more rebound damping for optimum control.
In this case, all I wanted was more height.
However, as we both know, the rebound is not adjustable on the DR so it's all bloody semantics anyway.
CU tomorrow

[Ocean1]

Right, for anyone who is interested, the static sag was 50mm with a spring length of 246 mm.

It's now 35 mm with a spring length of 239mm and will come back to about 50 mm with some baggage aboard.

This actually ties in quite well with the numbers that both Nordie Boy and Crisis Management suggested.

The bike is significantly more stable on the side stand too so, objective achieved. We will see what the ride is like on the weekend, but since all I have done in effect, is change the ride height, I don't expect to feel any difference.

Be interested to hear what you think about the change. Cranking the rear up 15mm on the KLX makes a big difference to steering.

[Crisis management]

Be interested to hear what you think about the change. Cranking the rear up 15mm on the KLX makes a big difference to steering.

Yup, it tank slaps at about 120........

I'm fairly light so with just me on it gets a bit vaque over 110 and keeps on getting vaquer (is that a word or should it be vaquerer?) until it wants to go look at bushes and othe interesting things not in the direction I want to go. Bit like a dog really, you know, Ooooh lets have a look at that....

Put 15kgs of gear on the back and it settles down and becomes stable, you'd think with 28 degrees of rake this wouldn't happen but it bloody well does.
The other contributing factor to this is the screen I have fitted. After extensive wind tunnel testing with cardboard & scissors (back & forth over the mangere bridge, handy having a motorway within 1km) I found that a small screen was workable but as soon as it got over 350mm high the front end got steered by the screen.

So, Bass shouldn't have much of a problem as he doesn't run with a screen and is slightly "bigger boned" than me. Be interesting to see tho...

Must hide now.

[Bass]

Be interested to hear what you think about the change. Cranking the rear up 15mm on the KLX makes a big difference to steering.

Any idea why?

It's a tiny change to the steering angle after all.

[Bass]

So, Bass shouldn't have much of a problem as he is slightly "bigger boned" than me.

Must hide now.


Bastard!!
True but Bastard anyway!!

[ducatijim]

The main effect is to increase the ride height.

However the 2 adjustments tend to be linked because the most common reason for a preload increase is more weight on the bike and very often, the extra weight requires more rebound damping for optimum control.


We have been over this crap time and time again. My comment relates to the second quote above, being the most common reason to raise the ride height.

As for the first, well I have never heard of increasing the RIDE height in order to shorten the SIDESTAND!!! Who is the engineer here? Get ur fucken angle grinder out, cut the cunt back then weld a bigger foot at the bottom. Done.:niceone:

[Ocean1]

Yup, it tank slaps at about 120........

I'm fairly light so with just me on it gets a bit vaque over 110 and keeps on getting vaquer (is that a word or should it be vaquerer?) until it wants to go look at bushes and othe interesting things not in the direction I want to go.

That's one of the negatives at the extreme end of fwd/aft sag adjustments. Sounds like yours is worse than most though. The KLX does get a more vague and willful if it's arse-up or nose-down but not that bad. The badness at the other end is a tendency to wash the front out, and that's more difficult to predict. And just as painful.

How did you come to discover the tankslapperofdoom tendency? were you trying for a lower seat height?


Any idea why?

It's a tiny change to the steering angle after all.

It is, and I agree that it seems an unreasonable effect for such a small variable. I think it's as much to do with the slight reduction in trail as the change in rake. I wouldn't expect a DR650 with 27deg rake to be as sensitive as CM has found, but there you go.

FWIW even smaller adjustments on the Buell produce quite large effects, presumably because of the very short wheelbase and 21 deg rake. 10mm down on the back changes the steering from a seriously sudden and surgically precise, (if a little twitchy) to almost cruiser-like, (slight exageration but you get the idea...)

[Crisis management]

How did you come to discover the tankslapperofdoom tendency? were you trying for a lower seat height?


I wouldn't expect a DR650 with 27deg rake to be as sensitive as CM has found, but there you go.



Tankslapper....a combination of rear ride height / rake and the screen I fitted. DR's are fairly light/vaque in the front IMHO and it obviously doesn't take much to tip the balance. I've not reduced the preload on mine as the springs are marshmellow enough as it is. I'm sure with some set up I could get rid of the tankslapping but it's not much of an issue as most backroads stuff is well below those speeds.

(I grew up on Kawasaki H1's and Suzi T500's so handling has never been something I stress about)

As far as being sensitive....this is Auckland your talking about, we're all new age sensitive types up here!

[Bass]

As for the first, well I have never heard of increasing the RIDE height in order to shorten the SIDESTAND!!! Who is the engineer here? Get ur fucken angle grinder out, cut the cunt back then weld a bigger foot at the bottom. Done.:niceone:

Well, while I claim to be an engineer, I never claimed to be a good one and I kinda thought that Mr Suzuki was pretty likely to be better than me. So I figured that when he designed the bike, he probably had all this stuff pretty much in balance. Having come to this conclusion, I thought it pretty unlikely that I should have to chop up the machine to get this sorted out.

There are a limited number of adjustments that he left for me to play with (sensible fellow) - suggest to me another adjustment I could use O wise guru.:girlfight:

On top of that, it was pretty much OK when delivered, but started to settle a bit during the last weekend excursion we attended, from which I conclude that the spring and linkages have settled a bit.

Besides, it's only short arse cow cockys whose ring pieces drag on the ground, that have to lower adventure bikes and hack side stands, is it not? (or women, but we won't go there)
:lol:

P.S. It's also why Mr Suzuki makes quads for cow cockys isn't it?

[Bass]

We have been over this crap time and time again. My comment relates to the second quote above, being the most common reason to raise the ride height.


Excellent!
I see that you retain some of the stuff I taught you!
I just thought that some stroppy heifer might have kicked you in the nuts again and caused you to forget it all.
I see I was wrong though and I humbly apologise.

[Ocean1]

I grew up on Kawasaki H1's and Suzi T500's so handling has never been something I stress about

Ah, quite.

Ain't modern bikes great, one doesn't actually need to stop for corners, get off, push it around and take off agin'. :whistle:

[Bass]

The badness at the other end is a tendency to wash the front out, and that's more difficult to predict. And just as painful.


Again I fail to comprehend, which is not all surprising and almost commonplace.
Why would this adjustment influence front end grip?

I can see that changing the rake influences the lean angle that the wheel adopts as it turns, but we are still talking miniscule changes.

[Bass]

Tankslapper....a combination of rear ride height / rake and the screen I fitted. DR's are fairly light/vaque in the front IMHO and it obviously doesn't take much to tip the balance.

I fiddled around with model aircraft for years - in particular the racing kind. Along the way, I learned a little about aerodynamics and stability. I strongly suspect that the screen is responsible for the much greater proportion of the problem, particularly since as you point out, the steering is pretty light anyway.

While on this topic, what symptoms was it that pushed you out on to the Mangere bridge with cardboard and scissors?

[tri boy]

[QUOTE=Bass;1373318]I fiddled around with model aircraft for years - in particular the racing kind. Along the way, I learned a little about aerodynamics and stability. I strongly suspect that the screen is responsible for the much greater proportion of the problem, particularly since as you point out, the steering is pretty light anyway.

...or that Ian's piddly little biceps couldn't hold a teaspoon of sugar in a stable manner, let alone a motorcycle handlebar:rofl:

[Crisis management]

While on this topic, what symptoms was it that pushed you out on to the Mangere bridge with cardboard and scissors?

I found the wind pressure on my chest a bit of a pain after a couple of hundred Kms so decided to experiment with a small screen, or as hairy arse below states, something about piddly little biceps....

[QUOTE=tri boy;1373397...or that Ian's piddly little biceps couldn't hold a teaspoon of sugar in a stable manner, let alone a motorcycle handlebar:rofl:[/QUOTE]

You'll keep, boy, you'll keep.

How's it go, revenge is a dish best served cold?

[Ocean1]

Again I fail to comprehend, which is not all surprising and almost commonplace.
Why would this adjustment influence front end grip?

I can see that changing the rake influences the lean angle that the wheel adopts as it turns, but we are still talking miniscule changes.

It's complicated, (which is one way of saying I don't know) and there's more to it than the effect the simple geometry changes make. It's partly related to how modern dirt bikes work, and the need to weight the front wheel and the outside peg. If you don't get this technique right, (and I'm an expert at getting it not quite right) then you risk putting too much lateral force on the front.

Whether the theory is valid or not it helps me to imagine I'm forcing the front tyre into the ground, as opposed to simply leaning it in like you might on the road, which produces more sideways force. More rake and trail exacerbate the tendency, that's all, and because I learned on bikes that were a bit less radically optimised for MX style handling my style isn't quite right, and my reactions sometimes get me into trouble.

There is some insight to be gained by imagining an extreme case like a tradional chopper. Huge rake and trail. Imagine that leaned over in sub-optimal conditions, the steering required to turn it in is way more than that needed on a dirt bike. The tendency for the front to slide out is higher, and yet there's less weight on the front end to hold it.

[Bass]

You'll keep, boy, you'll keep.

How's it go, revenge is a dish best served cold?

I think that may be exactly what we are seeing - something to do with U-boats as I recall

[NordieBoy]

Any idea why?

It's a tiny change to the steering angle after all.

Moving the forks 3mm in the clamps of my XR250 makes a noticeable difference in the handling.

[ducatijim]

Well, while I claim to be an engineer, I never claimed to be a good one and I kinda thought that Mr Suzuki was pretty likely to be better than me.



P.S. It's also why Mr Suzuki makes quads for cow cockys isn't it?


If your 'Mr Suzuki' , engineer extrordinaire, could so badly fuck-up the design and building of the DR's so-called seat, wot makes you think he could get something as complicated as a sidestand correct???

Quads? short-arses??....u fucken try carrying 2x portable fence reels, 20kg of pigtails and the newborn calf all on your 2 wheeler at once.....if you can, then you are truely a better man than I.

[Bass]

If your 'Mr Suzuki' , engineer extrordinaire, could so badly fuck-up the design and building of the DR's so-called seat, wot makes you think he could get something as complicated as a sidestand correct???

Quads? short-arses??....u fucken try carrying 2x portable fence reels, 20kg of pigtails and the newborn calf all on your 2 wheeler at once.....if you can, then you are truely a better man than I.


You are getting a bit off topic there, aren't you mate?

Anyway, I seem to remember you doing all of that on a Honda 90 and that was built for short arses too.

PD here we come.

[Bass]

Moving the forks 3mm in the clamps of my XR250 makes a noticeable difference in the handling.


I can't even get close to understanding why.

[warewolf]

I can't even get close to understanding why.Why wouldn't it? We are talking about subtle differences here.

A couple of turns of preload, a click or two of damping adjustment, a couple of psi in the tyres, position of the rear axle in the chain adjusters, etc etc. All very minor things that can make a big difference.

[Transalper]

I'm sorry, not sure i picked up all the things under descusdsion here while skimming the thread...
re side stand length, you guys do know don't you that they supply two side stand lengths, one for standard ride height and a shorter one for when the bike is set to the lowered position.

[cooneyr]

Call me a nOOB but - ride the damn things for a good year or so till your actually getting to the point pushing the limits of the stock bike, then figure out what is wrong and deal with it. You need to establish a base line and if your skills wrt a particular bike are still improving significantly your not going to be able to do this.

I know this isnt going to help you Bass but others tend to spend to much time farkling and not enough time riding if you ask me (I know ya didnt :chase:). My speed and confidence on the DR has improved significantly over the past year and I've not changed a thing (OK got the forks serviced - seals and oil replaced). I don't even remotely consider myself ready for major changes such as ohlins (not that I'd ever do that anyway). Might do a stiffer shock spring and shock rebound revalve middle of the year but not sure I need it yet.

Cheers R

[Bass]

Why wouldn't it? We are talking about subtle differences here.

A couple of turns of preload, a click or two of damping adjustment, a couple of psi in the tyres, position of the rear axle in the chain adjusters, etc etc. All very minor things that can make a big difference.

So I believe - I'm just trying to get my head around the physics, geometry and mathematics of why. So far, the things I am being told, it seems to me that the result is out of all proportion to the size of the adjustment.

[Bass]

I'm sorry, not sure i picked up all the things under descusdsion here while skimming the thread...
re side stand length, you guys do know don't you that they supply two side stand lengths, one for standard ride height and a shorter one for when the bike is set to the lowered position.

Yep, DJ's bike has been fed the lowering kit - that's what a bit of the earlier banter was all about (short arse references etc)

[Bass]

Call me a nOOB but - ride the damn things for a good year or so till your actually getting to the point pushing the limits of the stock bike, then figure out what is wrong and deal with it. You need to establish a base line and if your skills wrt a particular bike are still improving significantly your not going to be able to do this.

I know this isnt going to help you Bass but others tend to spend to much time farkling and not enough time riding if you ask me (I know ya didnt :chase:). My speed and confidence on the DR has improved significantly over the past year and I've not changed a thing (OK got the forks serviced - seals and oil replaced). I don't even remotely consider myself ready for major changes such as ohlins (not that I'd ever do that anyway). Might do a stiffer shock spring and shock rebound revalve middle of the year but not sure I need it yet.

Cheers R

I don't disagree. However Jamie and I are off to OZ for 2 months later this year and will do around 18,000 km, mostly on 4WD tracks and heavily loaded. The standard rig just won't hack it and so the mod's have to happen regardless of my experience (or lack of it).

[warewolf]

So I believe - I'm just trying to get my head around the physics, geometry and mathematics of why. So far, the things I am being told, it seems to me that the result is out of all proportion to the size of the adjustment.Maybe I can explain it geometrically... :D

If the result curve is plotted, at some point there is a 'knee' where for small inputs there is a dramatic difference in output. Bikes are set up at that knee. The further a particular setting (or range of adjustment) is from that knee, the less effect it will have, and vice-versa.

Consider a conical needle valve. At closed or nearly so, the size of the opening increases greatly as the needle is backed out, therefore so does the flow through the valve. Typically after a few turns, there is very little difference in response as the size of the opening goes from essentially 'infinite' to 'infinite plus some small increment = infinite'. In this particular example, some of the reason is that the orifice of the valve becomes the limiting factor, not the opening around the needle point. (Thanks RT.)

Zat what you were asking?

[Ocean1]

Maybe I can explain it geometrically... :D


S'not geometry, that's hydraulics.

And you're saying he needs a bigger orifice?

[Bass]

Maybe I can explain it geometrically... :D

If the result curve is plotted, at some point there is a 'knee' where for small inputs there is a dramatic difference in output. Bikes are set up at that knee. The further a particular setting (or range of adjustment) is from that knee, the less effect it will have, and vice-versa.

Zat what you were asking?

Sorry but no. Close though.
Saying that at some point there is a 'knee' where for small inputs there is a dramatic difference in output, is simply putting it in other words.
What I am trying to figure out is why there is a knee, (in your valve example, it's a simple geometrical ratio thing). In fact, I don't accept that there is a knee. for the adjustment to have a sensitive response, the curve (or part curve) just needs to have a large slope or dy/dx = a large number.
However, that's just me being pedantic and I understand what you are trying to say. I am interested in understanding why the machine is particularly sensitive to the adjustments over some small part of their range, rather than a different way of saying that it is.

It also seems to me to be a tad dangerous. For example, Ocean1's experience of a 15 mm change in rear end static sag significantly affecting front wheel grip is not reassuring (and that's ignoring the size of his orifice).

[ducatijim]

Moving the forks 3mm in the clamps of my XR250 makes a noticeable difference in the handling.


I move my forks 45mm thru the clamps, depending on whether I am gravel riding or doing a track day. Same wheel, differant tyres. Makes fuck all diferance. 3mm ????, can't see it on a 27' rake(approx?) makin any differance. Now, on a Ducati 999, oh yes.............

[ducatijim]

You are getting a bit off topic there, aren't you mate?

Anyway, I seem to remember you doing all of that on a Honda 90 and that was built for short arses too.

PD here we come.

Off topic? you asked how to make the bitch sit up some more, I provided the answer, and pointed out that Mr Suzuki may not always be right, spot on topic as I seez it.

Honda postie?.....yeah, only 1 reel and the fuckn calf WALKED. You nowwill have every lanky Postie in the country after YOUR arse!!!!

[Bass]

You now will have every lanky Postie in the country after YOUR arse!!!!

Yeah!
Warewolf and Ocean have already warned me that I need a bigger orifice.

[Ocean1]

Sorry but no. Close though.


Beer in mind it's not a DR650. Can't recall the salient geometric details but the rake is steeper to start with.

Worth noting however that a fore/aft attitude change isn't just changing rake, it's also changing trail and weight bias. Slightly to be sure, but the changes all aim the same way wrt behaviour. You’ll be familiar with the effect compound variables can have on a process…

And yes, wrt my orifice I have been made abundantly aware that ignorance is bliss.

[warewolf]

What I am trying to figure out is why there is a knee, (in your valve example, it's a simple geometrical ratio thing). In fact, I don't accept that there is a knee. for the adjustment to have a sensitive response, the curve (or part curve) just needs to have a large slope or dy/dx = a large number.Wasn't quite sure what you were asking. However, to continue on this theme, by sensitive I meant d2y/dx2 (delta dy/dx) changes markedly. dy/dx can be as large as you want and still be considered consistent, not sensitive.


I am interested in understanding why the machine is particularly sensitive to the adjustments over some small part of their range, rather than a different way of saying that it is.

It also seems to me to be a tad dangerous. For example, Ocean1's experience of a 15 mm change in rear end static sag significantly affecting front wheel grip is not reassuring The answer is that it is a complex system of inter-related functions aka "I don't know" or "it just is" :laugh:. And yes, it can be dangerous making changes.

[warewolf]

I move my forks 45mm thru the clamps, depending on whether I am gravel riding or doing a track day. Same wheel, differant tyres. Makes fuck all diferance. 3mm ????, can't see it on a 27' rake(approx?) makin any differance. Now, on a Ducati 999, oh yes.............So the DR is away from the knee, the 999 right on it. QED.

Enduro riders change their pull-through by 2-5mm all the time, depending on conditions. eg Woodhill sand whoops are better with more rake, weaving between the trees is better with less. You can feel the difference quite easily - and you want it.

[Bass]

Wasn't quite sure what you were asking. However, to continue on this theme, by sensitive I meant d2y/dx2 (delta dy/dx) changes markedly. dy/dx can be as large as you want and still be considered consistent, not sensitive..

Yep. We are on the same page.


The answer is that it is a complex system of inter-related functions aka "I don't know" or "it just is" :laugh:. And yes, it can be dangerous making changes.

......and probably something to be thrashed out over a beer and a few text books rather than in here.

[warewolf]

......and probably something to be thrashed out over a beer and a few text books rather than in here.Thinking the same thing myself :apint:

[Bass]

Be interested to hear what you think about the change. Cranking the rear up 15mm on the KLX makes a big difference to steering.

Right, just to complete this discussion and to report what I found having just done about 1000 km over the weekend with the rear end cranked right up and about 15 kg of luggage on the back.
We covered a wide variety of terrain, I noticed no change in the handling and it was much more stable on the stand.

[GaZBur]

Call me a nOOB but - ride the damn things for a good year or so till your actually getting to the point pushing the limits of the stock bike, then figure out what is wrong and deal with it. You need to establish a base line and if your skills wrt a particular bike are still improving significantly your not going to be able to do this.

I know this isnt going to help you Bass but others tend to spend to much time farkling and not enough time riding if you ask me (I know ya didnt :chase:). My speed and confidence on the DR has improved significantly over the past year and I've not changed a thing (OK got the forks serviced - seals and oil replaced). I don't even remotely consider myself ready for major changes such as ohlins (not that I'd ever do that anyway). Might do a stiffer shock spring and shock rebound revalve middle of the year but not sure I need it yet.

Cheers R
I'm with you on this. I am new too but am also pushing the bikes limits ok. I just skimmed this thread and really dont understand the geometry and changes that result from alteations.
I did have a problem with the standard set up shock as sliding into corners on the Motard track the DR shuddered with the back skipping and not maintining a smooth slide. A bike mechanic told me to just wind the spring preload as hard as it will go as it was way too soft. I wound it all the way and if fixed the problem. It is still ok for road use like that. I loaded it up and rode central and also found it handled the gravel and dirt tracks ok set like that. Seems to be OK in most situations so don't see the point in spending money on new shocks that could be better spent on tyres. Maybe when I get real good and know exactly what does what I will look into further but seems too much like hard work for little gain to me!

CORRECTION EDIT- I said I wound it up all the way - in fact it is more like 3/4 now I have checked.

[warewolf]

Your motard racing application is pretty narrow. From everything I've ever read, if you've got that much preload on a spring, the spring is way, way too soft and will cause more problems than it will solve. Note that a steady slide means you have LESS grip (slide, slide, slide) than when it was shuddering (grip, slide, grip, slide). This is the same as what drifters want: no grip for any easy continuous predictable slide.

I must take your admission that you are "new" as a bit of a negative against your comment that it is "ok for road use". Sorry to be so negative but although this configuration sounds like it is working for you, I wouldn't recommend it for everyday use!

[Bass]

Seems to be OK in most situations so don't see the point in spending money on new shocks that could be better spent on tyres. Maybe when I get real good and know exactly what does what I will look into further but seems too much like hard work for little gain to me!

The reason we are fitting new shocks is that we are going to do Outback Oz and at times will be 300 + km from mechanical help, heavily loaded, on some really rough tracks. So the change is as much about reliability as it it is about performance.

[cooneyr]

The reason we are fitting new shocks is that we are going to do Outback Oz and at times will be 300 + km from mechanical help, heavily loaded, on some really rough tracks. So the change is as much about reliability as it it is about performance.

I know they are a bunch of numptys but don't watch Charlie and Ewan's latest, The Long Way Down. Ewan and the camera man managed to blow the seals and or root the springs on two Ohlins shocks (they swaped out the BMW shocks) each during the trip. The fact that they were carrying umpteen million tonnes of gear and aren't the best riders maybe, just maybe had something to do with it. Don't think Charlie had any issues with his shock (well not that was included on the DVD anyway).

Cheers R

[GaZBur]

Your motard racing application is pretty narrow. From everything I've ever read, if you've got that much preload on a spring, the spring is way, way too soft and will cause more problems than it will solve. Note that a steady slide means you have LESS grip (slide, slide, slide) than when it was shuddering (grip, slide, grip, slide). This is the same as what drifters want: no grip for any easy continuous predictable slide.

I must take your admission that you are "new" as a bit of a negative against your comment that it is "ok for road use". Sorry to be so negative but although this configuration sounds like it is working for you, I wouldn't recommend it for everyday use!

OOPS! I said I wound it up all the way - in fact I stopped at 3/4 as it fixed the problem so will go back and edit my original post . I did find on the rutted gravel roads and moderate off roading it kept line at this. I was also told the standard spring was probably too soft as well so that probably why its working OK wound up to that level.
Perhaps I will look online for a "Setting up suspennsion for dummies!" as most of the terms used in this forum go over my head. I dont even know how to measure static sag.

[warewolf]

Perhaps I will look online for a "Setting up suspennsion for dummies!" as most of the terms used in this forum go over my head. I dont even know how to measure static sag.Good stuff. Google it, there's plenty of articles online.

[Ocean1]

I'm with you on this. I am new too but am also pushing the bikes limits ok. I just skimmed this thread and really dont understand the geometry and changes that result from alteations.
I did have a problem with the standard set up shock as sliding into corners on the Motard track the DR shuddered with the back skipping and not maintining a smooth slide. A bike mechanic told me to just wind the spring preload as hard as it will go as it was way too soft. I wound it all the way and if fixed the problem. It is still ok for road use like that. I loaded it up and rode central and also found it handled the gravel and dirt tracks ok set like that. Seems to be OK in most situations so don't see the point in spending money on new shocks that could be better spent on tyres. Maybe when I get real good and know exactly what does what I will look into further but seems too much like hard work for little gain to me!

CORRECTION EDIT- I said I wound it up all the way - in fact it is more like 3/4 now I have checked.

So you need to be good to take advantage of correct set-up?

I'm not very good, but I'd say my ferkling saved me a bunch of skin once I understood what was what.

Besides, I'm a techie, if it's adjustable I'll do it from pured cussed curiosity. Not adjust suspension? Might as well give a kid a bag of lollies and tell him not to eat 'em...

[NordieBoy]

I dont even know how to measure static sag.

First you need a nylon jersey and a balloon...

[Crisis management]

Try this link http://www.kiwibiker.co.nz/forums/showthread.php?t=36169&highlight=useful+suspension+guide as it sets out the basics in an understandable manner.

Well, for my first attempt to link anything thats an interesting result! Technophobes rule!

[Bass]

First you need a nylon jersey and a balloon...

And a banana about that colour for the fine adjustment.